Free Shipping error in Calculator

[marcosdsdba]

Steps to reproduce

1. Install Magento from develop branch.
2. Magento 2.3.1
3. Create Cart Price Rule
   Conditions
   Total Items Quantity equals or greater than 2

Action
Percent of product price discount
Discount Amount 0
Maximum Qty Discount is Applied To 0
Discount Qty Step (Buy X) 0
Apply to Shipping Amount YES
Discard subsequent rules YES

Expected result

1. Free Shipping

Actual result

1.Negative value causes NAN,N

In line 292 in Validator.php method getShippingAmountForDiscount() doesn't exists ?????

Another method not found is getBaseShippingAmountForDiscount();

See https://github.com/pepe1518/magento2/blob/master/vendor/magento/module-sales-rule/Model/Validator.php#L292